This invention generally relates to fusing members and, more specifically, the present invention relates to processes for the preparation of fuser members like fuser rolls wherein the coating applied to the fuser member contains a coating mixture of VITON.RTM., and an aliphatic alcohol like methanol. By adding the alcohol to the coating mixture, the life thereof, especially the pot life, can be increased to from about 4 to about 24 hours, and the solids content of the flow coating mixture can be increased to, for example, about 30 percent in embodiments. High solids contents of the fuser roll flow coating mixture, most typically at 25 weight percent solids, comprised of VITON GF.RTM. (available from E. I. DuPont, 60 parts, 20.33 weight percent), magnesium hydroxide (Merck and Company, MAGLITE D.TM., 1.2 parts, 0.407 weight percent), calcium hydroxide (Baker reagent grade, 0.6 part, 0.203 weight percent), copper oxide (American Chemet: 13600, 9 parts, 3.05 weight percent), VITON CURATIVE 50.RTM. (DuPont, 3 parts, 1.02 weight percent), methyl isobutyl ketone (197.78 parts, 67 weight percent), and methanol (Fisher Scientific, 23.62 parts, 8 weight percent), enables, for example, the flow coating application of 8 mil thick fuser roll coatings to be obtained more economically and specifically with fewer passes compared with spray painting of mixtures most typically selected, such as about 8 weight percent solids VITON GF.RTM. (15.7 parts, 6.50 weight percent), MAGLITE D.TM. (0.313 part, 0.13 weight percent), calcium hydroxide (0.1567 part, 0.065 weight percent), copper oxide (2.351 parts, 0.976 weight percent), VITON CURATIVE 50.RTM. (0.784 part, 0.325 weight percent), methyl isobutyl ketone (221.6 parts, 92.0 weight percent), and no alcohol like methanol.
Advantages of the fuser members of the present invention include avoiding or minimizing offsetting of molten toner images during fusing processes required to fix toner images to paper and plastic, improved fusing latitude, reduction in offsetting from preprinted forms, high thermal conductivity, and providing a high water contact angle, for example between 90.degree. and 95.degree., to release surface in those areas where the fluoroelastomer coating normally interacts with paper and fused toner images. Enhanced release of molten toner from the fuser roll can thus result. Moreover, the fuser coatings of the instant invention allow for conformable toner image fusing enabling matte images selected specifically in marketing studies for their appearance.
The types of components, such as rolls, that can be provided with the coatings of the present invention are illustrated, for example, in U.S. Pat. Nos. 4,373,239 and 4,518,655, the disclosures of which are totally incorporated herein by reference.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member, and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles and pigment particles, or toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support which may be the photosensitive member itself or other support sheet, such as plain paper.
The use of thermal energy for fixing toner images onto a support member is known. To fuse electroscopic toner material onto a support surface permanently by heat, it is usually necessary to elevate the temperature of the toner composition to a point at which the constituents of the toner material coalesce and become tacky. This heating causes the toner to flow to some extent into the fibers or pores of the support member, such as paper. Thereafter, as the toner cools, solidification of the toner causes it to be firmly bonded to the support.
Typically, the thermoplastic resin particles are fused to the substrate by heating to a temperature of between about 90.degree. C. to about 160.degree. C. or higher depending upon the softening range of the particular resin used in the toner. It is undesirable, however, to raise the temperature of the substrate substantially higher than about 200.degree. C. because, for example, of the tendency of the substrate to discolor at such elevated temperatures, particularly when the substrate is paper.
Several methods for the thermal fusing of electroscopic toner images have been described in the prior art. These methods include the application of heat and pressure substantially concurrently by various means like a roll pair maintained in pressure contact, a belt member in pressure contact with a roll, and the like. Heat may be applied by heating one or both of the rolls, plate members or belt members. The fusing of the toner results when the proper combination of heat, pressure and contact time are provided.
During operation of a fusing system in which heat is applied to permit thermal fusing of the toner particles onto a support, both the toner image and the support are passed through a nip formed between the roll pair, plate, or belt members. The concurrent transfer of heat and the application of pressure in the nip effects the fusing of the toner image onto the support. It is important in the fusing process that no offset of the toner particles from the support to the fuser member takes place during normal operations. Toner offset onto the fuser member may subsequently transfer to other parts of the machine or onto the support in subsequent copying cycles, thus increasing the background or interfering with the material being copied. This is referred to as "hot offset" and occurs when the temperature of the toner is increased to a point where the toner particles liquefy and a splitting of the molten toner takes place during the fusing operation with a portion remaining on the fuser member. The hot offset temperature, or degradation of the hot offset temperature is a measure of the release property of the fuser roll, and accordingly, it is desirable to provide a fusing surface, which has a low surface energy to provide the necessary effective release. To insure and maintain good release properties of the fuser roll, it has become customary to apply release agents to the fuser members to ensure that the toner is completely released from the fuser roll during the fusing operation. Typically, these materials are applied as thin films of, for example, silicone oils to prevent toner offset.
Described in U.S. Pat. No. 4,264,181, U.S. Pat. No. 4,257,699 and U.S. Pat. No. 4,272,179, all commonly assigned to the assignee of the present application, the disclosures of which are totally incorporated herein by reference, are fuser members and certain release agents. These patents describe specific fuser members and methods of fusing thermoplastic resin toner images to a substrate wherein a certain polymeric release agent having functional groups is applied to the surface of the fuser member. The fuser member comprises a base member having an elastomeric surface with a metal containing filler therein which has been cured with a nucleophilic addition curing agent. Exemplary of such a fuser member is an aluminum base member with a poly(vinylidenefluoridehexafluoropropylene) copolymer cured with a bisphenol curing agent with lead oxide or copper oxide filler dispersed therein and utilizing a mercapto functional polyorgano siloxane oil as a release agent. In these fusing processes, the polymeric release agents have functional groups, also designated as chemically reactive functional groups, which interact with the metal containing filler dispersed in the elastomer or resinous material of the fuser member surface to form a thermally stable film which releases thermoplastic resin toner, and which prevents the thermoplastic resin toner from contacting the elastomer material itself. The metal oxide, metal salt, metal alloy or other suitable metal compound filler dispersed in the elastomer or resin upon the fuser member surface interacts with the functional groups of the siloxane polymeric release agent. Preferably, the metal containing filler materials do not cause degradation of or have any adverse effect upon the polymeric release agent having functional groups. Because of this reaction between the elastomer having a metal containing filler and the polymeric release agent having functional groups, excellent release and the generation of high quality copies are obtained even at high rates of speed, such as 100 copies per minute, of electrostatographic reproducing machines. With these VITON.RTM./lead oxide, or VITON.RTM./copper oxide members, an oxide of low volume fraction is added to enable a specific functional release agent to react with it and thereby coat the silicone polymer oil like a polysiloxane, while with the present invention in embodiments the fillers, which are preferably selected in amounts of from about 5 to 20 weight percent based on the amount of fluoroelastomer rubber, are covered with a mercapto terminated silicone oil, rather than the polysiloxane oil. Thus, with the present invention improved toner and oil release is achieved from the fuser roll. When the copper oxide is omitted from the formulation, an amino-terminated silicone oil is used to coat the fluoroelastomer on the fuser roll.
The use of polymeric release agents possessing functional groups, which interact with a fuser member to form a thermally stable, renewable self-cleaning layer having superior release properties for electroscopic thermoplastic resin toners, is described in U.S. Pat. Nos. 4,029,827; 4,101,686 and 4,185,140, all commonly assigned to the assignee of the present invention. Disclosed in U.S. Pat. No. 4,029,827 is the use of polyorgano siloxanes having mercapto functionality as release agents. U.S. Pat. Nos. 4,101,686 and 4,185,140 are directed to polymeric release agents having functional groups such as carboxy, hydroxy, epoxy, amino, isocyanate, thioether and mercapto groups as release fluids. The disclosures of all of the aforementioned patents are totally incorporated herein by reference.